Explosive cutting tool



y 1960 w. G. SWEETMAN 2,935,944

EXPLOSIVE CUTTING TOOL Original Filed March 2 1948 as I I 29 a aa 1% I I D ,-IO

w. e. SWEETMAN 20 5 2o INVENTOR.

l4 BY I ATTORNEY abandoned. 1

Q the well.

'Thisinve'ntion relates to a cutting-tool forsevering pipe. More particularly, the invention pertains to a tool adapted to employ a detonating explosive charge for,

cutting pipe,.and similar tubular objects, in a well. This application is a continuation of my co-pending US. application Serial No. 12,543, filed March 2, 1948, now

' iIn'my co-pending application,'Serial No. 709,246, filed November 12, 1946,-now Patent No. 2,587,244, issued February. 26, 1952, there are disclosed methods and apparatus for cutting various objects and particularly for cuttingtpipe .in"the well 'by meansof a detonating expl'osive-l chargerwhich ,is preformed to a configuration correspondingto the. line of the cut to be made and whichlias'the :fa'ceQWhich is directed toward the object to be cut, dished. or concaved so that'upon detonation,

generatedhigh velocit-ygas'es will strike the object to be cut in a narrow jet along theline of the cut and perform the cutting" of the object by means of the jet itself.

. More specifically, in the aforementioned application there is described apparatus for cutting a well pipe, or

thelike, by means of a ring-shaped detonating explosive, the periphery of which is comically, or otherwise dished or concavedin a suitable manner, and suitably supported in a cylindrical body which is adapted to be'lowered-into a well casing to the point where the cut is to be made, whereupon the explosive charge may be detonated and a radially projected circular jet of the resulting gases directed against the innersurface of the pipe to effect the severing thereof. 7

:Such methods and apparatus have now been put tov extensive and successful commercialvuse and-this inven tion is directed particularly to improvements in the form of the tool employed, particularly for the cutting of well casing or other pipe in a well. It is found, for example, that when cutting pipe in the manner described, the tool which normally carries the-ring-shaped explosive charge mounted in the peripherylthereof,,will be severed at approximately the line where the charge is mounted. The portion of the. tool immediately adjacent and below the explosive charge will be destroyed or severed and lost in Moreover, it has been found that with such tools of the earlier design, the shock of the'e'xplosion may bulge or, otherwise damagethe remaining portion of the tool and connected mechanism, and since the clearance between the tooland the pipe is necessarily made quite small, this portion of the tool may become lodged in thewell and be'diflicult to remove, or may otherwise become .so damaged that it may not be readily re-used.

Accordingly, it is a principal-object, of the present invention to provide an improved design for such'cutting "I tools which overcomes, damage tothe unsevered portion of the tool.

' It'is an important object to provide. an improved form of cutting tool employing shaped explosive charges for efiecting the desired cutting operation. l

l additional importantobject is to provide an imnited States atent means of shaped explosive charges.

Another object is to provide an improved form of explosive cutting tool which is adapted to absorb the shock attendant upon detonation of the explosive to thereby minimize the damage to the tool and its supporting mechanism; Q 4 V V i I A more specific object is to provide a cutting tool in accordance with this invention, wherein a recoil absorbing mechanism is interposedbetween the explosive-carrying head and the elements employed for suspendingit in a well.

Other and more specific objects and advantages of this invention will become apparent from .the following detailed description when read in conjunction with the accompanying drawings which illustrate a useful embodiment in accordance with this invention.

In the drawings:

Fig. 1 is a longitudinal sectional view through a cutting {Ii-1;

tool in accordance with this invention;

Fig. 2 is a view similar to Fig. 1 showing parts o fthe i i 7 tool in their relative positions following *detonation of the explosive charge;

Fig. 3 is a cross-sectional view taken along line 3-3 I of Fig. 1;

Fig. 4 is a view showing the tool dis casing preparatory to cutting the casing.

Referring to the drawings, the improved cutting tool, in accordance with the illustrative embodiment of this, invention, comprises agenerally' cylindrical head mam: her-10 which is adant ed'to carry the explosive charge, a I

generally tubular cylinder member ll.telescopically'connected to the head member in sueha manner. as'to. per mit relative longitudinal movement between the 'mem: bers, and resilient means, such as a coil spring 12, mounted in compression between members 10 andv 1 1 toserve as a shock absorber or recoil cushioning means between members 10 and 11.

A More particularly, head member 10 is in the form of generally cylindrical solid body preferably constructed'of metalfsuch as steel; but which may be constructed of any other suitable solid material such as solid plastic molded or' machined to -the desired shape. Oneend of body member 10 is; reduced in diameter to form ashank 13 while the opposite endicarries an externallylflthreaded boss 14 by means of which afcone shaped. cap 15, which of body member 10 and adapted to form a fluid tight seal between the body member and rim 17; The end of body member 10 adjacent cap 15 is provided with an annular recess 19 extendingjinwardly from "the exterior of the body and dimensioned to receive any explosive charge of the desired size to be carried by the device; A ring-shaped hollowed explosive charge 20, composed of a suitable detonating chemical of well known character, is seated in recess 19. This form oficharge, when detonated, is adapted to generate a radially directed circular jet of'gases which will cut through rim 17 and sever the pipe in which the tool is inserted. The specificdetails of charge 20 have been described inthe aforementioned applications and in themselves do not roan-(s part of this invention. A recess 21, of generally tubular shape, is provided in body member 10 communicating radially witha point along the inner wall of recess '19.-

Recess 21 'isfadapted to receive an explosive pellet 22 in abutting relationship'to the explosive chargeZO to serve as I posed the well i a booster for the latter. The arrangement, as best seen in Fig. 3, wherein the booster pellet 22 is disposed in contact with the inner periphery of charge at a single point of relatively small area inherently acts to'cause the detonation wave in charge 29 to propagate circumferentially in both directions from the booster pellet so that there is no interference with the detonation wave except at a point diametrically opposite the booster charge. This arrangement results in the formation of an annular cutting jet which will produce a clean continuous out throughout the pipe circumference.

At the point where body member 10 is reduced in diameter to form shank 13, there is provided an annular shoulder 23 on which is mounted a ring 24- CQllgtliqptfid; of rubber, or other resilient material, which is employed for purposes to be described hereinafter. A fuse receptacle 25 is bored longitudinally in the upper end ofi shank 13 and is continued in the form of an elongated narrow passageway 26 which extends to a point in body member 10 adjacent the inner end of recess 22. An electrical fuse plug 27, having a suitably insulated conductor pin 28 extending axially therethrough, is adapted to be screwed tightly into. receptacle 25, and includes an elongated detonating fuse 29 of a type conventionally employed for detonating high explosive charges. Fuse 29 is electrically connected in a suitable and conventional manner to connector pin 28 and extends from the lower end of receptacle 25 through passageway 26 to a point adjacent e inne e of o t r Pe le 2?- Cylinder ber 1 ich s. Pr ab y Q5 metal ic construction, has an internal diameter slightlygreater than the external diameter of shank 13, whereby the, upper end of the latter may be inserted into the open end of cylinder member 11 for longitudinal movement therein. The, external diameter of cylinder member 11 is preferably made approximately equal to that of body member 10 so that'the, tool as a whole will have a substantially uniform external diameter. A plurality of angularly spaced elongated slots 30 are cut through the Wall of the cylinder member. Studs 31 are adapted to extend through slots 30 and to be screwed into the portion of shank 13 extending into cylinder member 11. With this arrangement it will be seen that relative longitudinal movement may occur between cylindermember 11 and shank 13, which is limited by the engagernentofthe upper and lower ends of slots 30 with studs 31, Coil spring 12, which is preferablyof relatively heavy con-- struction and of high compressive strength, is mounted in compression between the upper end of shank 13 and; a

head 32 carried by the upper end of cylinder member 11.'

Coil spring 12 will normally tend to urge members 10 and 11 apart and resist relative movement of these parts, toward each other. Head 32 is provided at its upper end with a hollow internally threaded box portion 33. An electrical contact member, designated generally by the numeral. 34, is mounted axially of head 32 and extends into box portion 33. A flexible electrical lead 35 connects contact member 34 with contact pin 28 of the fuse plug. A plurality of angularly spaced flexible fingei s 36 extend upwardly and radially outwardly from the surface of head 32 and are of such length that when in normal position, a circle enclosing their outer ends will be some-- at larger in di ete th h bf e P pe n. which he tool is to be used. A tubular rod 37 is provided with a threaded pin member 38 adapted to be secured in box; portion 3 d h s h l r 9- n. he l w r nd of which is mounted. an electrical contact member des; ignated generally by the numeral 40, of suitable construction adapted to make, electrical contact with contact member 34 when pin member 38. is screwed. into box portion 33, An electrical cable 41 is threaded through bore.

39 and is connected to contact member 40. Cable 41' which is adapted to carry current to fuse 29' also supports the cutting tool and is employed to lower the tool in a well. It will be understood that cable 41 will be connected to a suitable source of electric current and conventional switch means (not shown) located on the surface and operative in the usual manner to initiate the flow of current to fuse 29. Rod 37 is preferably constructed of heavy metal and is employed as a sinker or weight-supplying device in order to overcome the buoyancy of the tool, particularly when it is being run in a well casing which is filled with fluids such as drilling muds. One or more sections of rod 37 may be employed to provide whatever weight may be required for this purpose.

In assembling the cutting, tool preparatory to lowering in a well, booster pellet 22 will be inserted in recess 21 and explosive charge 20, performed to the desired ring shape and normally enclosed within a suitable housing of corresponding shape, will he slipped over the lower end of body member 10 and seated in recess 19. Cap 15 will then be screwed; on boss 14 to hold charge 20 firmly in place and, by means, of rim 17, form a fluid-tight closure about the periphery of; the charge; Ring 24will he slipped oyer the upper end of shank 13 and seated on shoulder 23, Fuse plug 27. and fuse 29 will be installed as a unit in shank 13. Contact member 34, having one end of lead 35 previously connected thereto, will have been installed in head 32. Coil spring 12 will be inserted in the bore of cylinder member 11, and the other end oi lead. 35 will be soldered or otherwise suitably connected to, contact pin 28, The upper end of shank 13 ill then be. inserted in the open end of cylinder member 11; against the lower end of spring 12 and studs 31 will be, inserted throughv slots30 and screwed into the inserted end of the shank. Fingers 36 will be installed. in head 32. One; or more, of, the rods. 37 will in the meantime, have been assembled and connected to the end of cable 41, and when pin member 38 isscrewed into box portion 33 the, tool will be ready for lowering in a well.

With the tool thus assembled, it will be lowered on cable 41 into a well casing 42 (Fig. 4). As the tool movesdownwardly through the casing, fingers 36 will be. compressed inwardly sons to. slide through the casing. When the: tool reaches the approximate area of the cut to. belmade, which will normally be along a casing section. previously selected from suitable measurements, the tool will be drawn upwardly until the first joint in the casing, above the. point to which. the tool was initiallylowerecl, is contacted by fingers 36, whereupon the fingers will expand into the space or crevice usually prescnt between the ends of adjacent sections of the casing where they: are. inserted in a conventional coupling 43. The outer ends of the fingers 36 will thereby lodge against the lower end of the upper one of the adjacent casing sections and will resist further upward movement of the tool under any normal strain applied to the cable. This will fix the position of the. cutting tool relative to the particular casing section which was selected to-be cut. The electrical initiator at the. surface may now be actuated to. set off fuse 29. The latter will detonate booster pellet; 22 which will, in turn, detonate main charge 20. The latter, in response to the single, small area point ofccntact with booster pellet 22, will generate the jet of cutting gases which will effect the desired severing of the casing.

When the detonation occurs, the lower portion ofbody 10 will normally be severed or destroyed, While the remainder of bodyltl will recoil upwardly. Fig. 2- illus-. trates the position of the parts of the tool up on recoil following detonation of the charge. It will be seen that shank l3 has'moved inwardly of cylinder member 11, compressing spring'12, which thus absorbs the shock of the recoil. Atthe same time the lower rim of cylinder member 111 will contact resilient ring 24 which acts as a cushion therefor to prevent battering or deformation of the end of the cylinder member. The remaining parts, of the tool, which are thus protected against damage, may

.then be withdrawn from the well, only sufficient'strain, being necessary to be placed on cable- 41 to'bend fingers: 336 sufliciently to cause them to be pulled out .of theirfcon: tact withv the casing. Since'thesefingers are normally,

constructed of relatively light wire, no great strain on a cable 41 will be required. When the tool has been thus withdrawn from'thewell, the remainder ofbodymem: ber-- will be disconnected from cylinder memberlll,v and all-of the latter and its supporting elements will beavailable for re-use merely by the connection ofa. new body member 10 carrying 'a fresh charge of explosive and a new fuse assembly. 7

It will-be understood that other specific forms of shock absorbing mechanisms maybe substituted for coil spring 12, as for example, a hydraulic or pneumatic type of shock absorber of well known design. .In many instances coil spring '12 may be eliminated and the shock absorbed entirely by a'resilient ringsuch'as ring24. 1 Other changes ,and alterations may also be made in the details of-the illustrative embodiment herein describedwithin the scope of the appended claims but without departing from the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. A toolfor cutting pipes ina well by means of explosives, comprising, a generally cylindrical body member adapted to be positioned longitudinally in the pipe and having mounted therein an annular explosive charge concentrically spaced about the longitudinal axis of the body member, a cylinder member telescopically engaged with said body member for limited relative longitudinal movement and having means on its outer end for connection to 'a suspending cable, and a recoil absorbing mechanism interposed between said body member and said cylinder member.

2. A tool for cutting pipes in a well by means of explosives, comprising, a generally cylindrical body member having mounted therein an annular explosive charge concentrically spaced about the longitudinal axis of the body member, a tubular cylinder member having one end telescopically engaged with said body member for limited 1 relative longitudinal movement, a head'for the opposite end of said cylinder member carrying a connector memher for connecting said cylinder member to "a suspending cable, and a'recoil absorbing element mounted in said cylinder member between said body member and said head.

3. A tool for cutting pipes in a well by means of explosives, comprising, a generally cylindrical body member having mounted therein an annular explosive charge concentrically spaced about the longitudinal axis of the body member, a tubular cylinder member having one end telescopically engaged with said body member for lirnitedrelative longitudinal movement, a head for the opposite end of said cylinder member carrying a connector member for connecting said cylinder member to a suspending cable, and a recoil absorbing element com-,

prising a coil spring mounted in said cylinder member in compression between said body member and said head.

4. A tool for cutting pipes in a well by means of ex-- plosives, comprising, a body member having mounted therein an annular explosivecharge concentrically spaced about the longitudinal axis of the body member and carrying electrical detonating means for said charge, a

connector member for connecting said'body member, to

a suspending cable and carrying means for forming an electrical connection between said detonating means and 'said' cable, means connecting said connector 'member to said body member for limited relative longitudinal movement, and a shock absorbing member interposed between said body member and said connector member.

5. A tool for cutting pipes in a well by means of explosives, comprising,-a generally cylindrical body member having mounted therein an annular explosive charge 7 concentrically spaced about the longitudinal axis of the body member and carrying electrical detonatingmeans for said charge, a cylinder member telescopically engaged with jsaid body member for limited relative longitudinal movement and having meansfor connection to a currentcarrying suspending cable, means carried by said cylinder member for forming an electrical connection between said detonating means and said cable, and a recoil ab-.

sorbing mechanism interposed between said body memf-i ably mounted on the lower end of said body having an;

upstanding rim to enclose; said charge, a tubular cylinder slidably enclosing the upper end of said ,body ,mem ber, inter-engaging elements connecting said cylinder member to said body member for limited relative longitudinal movement, a head for the opposite endof said cylinder member carrying a connectormember for "connecting said cylinder member to a suspending cable, and a coil spring mounted in said cylinder member in compression between said body member and said head.

7. A tool for cutting pipes in a well by means of explosives, comprising, a body member having mounted therein an annular explosive charge concentrically spaced about the longitudinal axis of the body member, a connector member for connecting said body member to a suspending cable, means connecting said connector member to said body member for limited relative longitudinal movement, and a shock-absorbing member interposed between said body member and said connector member, said shock-absorbing member being composed of resilient composition material.

8. A tool for cutting pipes in a well means of facing shoulder on said body about said stem portion,

a tubular member having its lower end telescopically enclosing said stem portion and connected thereto for limited relative longitudinal movement, means for connecting the upper end of said tubular member to a suspending cable, and a shock-absorbing member interposed between said shoulder and the lower end of said tubular member.

9. A tool for cutting pipes in a well by means of explosives, comprising, a generally cylindrical body member carrying a ring-shaped explosive charge seated in the periphery thereof, said body member having an upwardly extending stem portion of reduced diameter, an upwardly facing shoulder on said body about said stem portion, a tubular member having its lower end telescopically enclosing said stern portion and connected thereto for limited relative longitudinal movement, a head member for connecting the upper end of said tubular member to a suspending cable, a shock-absorbing member mounted in said tubular member between said stem portion and said head member, and a second shock-absorbing member interposed between said shoulder and the lower end of small body of a booster explosive disposed in contact with a single small area along a single small fraction of the circumferential length of the inner peripheral surface of said charge and projecting radially inwardly therefrom,

the remainder of said inner peripheral surface of said charge being free from contact with booster explosive,

and an initiating element disposed in contacttwith the inner end of said body of booster explosive.

ll. In a device for cutting pipe in a well, a cutting unit comprising aring shapedexplosive charge having an annular hollow-completely around itsou t'er periphery, an annular liner seated in' 'saidhollow, said charge having a single point of initiation of detonation comprising a pelletof booster explosive substantially smaller than the central opening through said charge, said pellet being ofis'et radially from the central axis of said charge and disposed in contact with a single small area along a single small fraction of the circumferential length of the inner peripheral surface of said charge, the remainder of said inner peripheral surface of said charge being free from contact with booster explosive, and an explosion initiating element in contact with said pellet.

12. In a device for insertion in a pipe for cutting such pipe, 2. cutting unit comprising a ring shaped explosive charge having an annular hollow completely around its outer periphery, an annular liner in said hollow, said charge having a single point of initiation of detonation comprising a small pellet of booster explosive positioned in contactwith a single small area along a single small fraction of the circumferential length of'the inner periph; ery of said ring shaped "explosive charge and extending. radially inwardly therefrom'withfthe inner end of said.-

Retenmcesv Cited n t e file of this pa en N TED STA ES A E S 2,415,814v Davis et al. Feb. 18, 1947; 2,494,256 Muskatet a1 Jan. 10, 1950 2,506,836. Kaltenberger May 9, 1950' 2,684,030 Muskat et a1. July 20, 19 54 

